Oligomeric and high-molecular conversion products of allophanic acid esters with nucleophilic compounds and low-molecular, oligomeric and high-molecular compounds with allophanate side and/or terminal groups, and the use thereof

ABSTRACT

Oligomeric and high molecular mass products of reaction of alkyl and aryl allophanates with nucleophilic compounds, and also low molecular mass, oligomeric and high molecular mass compounds containing lateral and/or terminal allophanate groups, and also the use of the reaction products and/or of the compounds in coating compositions, adhesives and sealing compounds or for producing films.

This application claims priority under 35 USC §120 upon InternationalPCT Application PCT/EP99 filed Aug. 27, 1999 and German PatentApplication DE 198 39 453.3, filed Aug. 29, 1998.

The present invention relates to novel oligomeric and high molecularmass products of reaction of allophanic esters with nucleophiliccompounds and also to novel low molecular mass, oligomeric and highmolecular mass compounds containing lateral and/or terminal allophanategroups. The present invention additionally relates to the use of thesereaction products and compounds in coating compositions, films,adhesives, and sealing compounds. The present invention further relatesto novel coating compositions, films, adhesives and sealing compoundswhich comprise the novel oligomeric and/or high molecular mass productsof reaction of allophanic esters with nucleophilic compounds and/or thenovel low molecular mass, oligomeric and high molecular mass compoundscontaining lateral and/or terminal allophanate groups. The presentinvention relates not least to novel processes for preparing thesereaction products or compounds.

Clearcoat materials for the automobile sector which comprise oligomersand/or polymers containing lateral and/or terminal carbamate(—O—C(O)—NH₂) groups are known from the patents EP-A-0 594 071, EP-A-0594 068, EP-A-0 594 142, WO 94/10212, WO 94/10211, WO 94/10213, DE-C-3634 780 and U.S. Pat. No. 5,098,947. They may be prepared by differentprocesses, which are described in these patents. It has, however, provenappropriate to prepare these oligomers and polymers containing lateraland/or terminal carbamate groups by reacting hydroxyl-containingoligomers and polymers with methyl carbamate. In some cases oftranscarbamation, however, the reactivity of methyl carbamate iscomparatively low, so that relatively high temperatures must be employedin order to obtain higher reaction rates. However, the highertemperatures may cause thermal damage to the products, after which theyare no longer suitable for use, for example, in clearcoat materials.

Low molecular mass and oligomeric compounds containing lateral and/orterminal carbamate (—HN—C(O)—O—R) groups are described in the patentsU.S. Pat. No.4,710,542 and EP-B-0 245 700 and also in the article by B.Singh and co-workers,“Carbamylmethylated Melamines, Novel Cross-linkersfor the Coatings Industry”, in Advanced Organic Coatings Science andTechnology Series, 1991, Volume 13, pages 193 to 207. These compoundscomprise reaction products of carbamates, especially alkyl carbamates,and melamine resins. These lateral and/or terminal carbamate(—HN—C(O)—O—R) groups are no longer capable of entering intocrosslinking reactions with the lateral and/or terminal carbamate(—O—C(O)—NH₂) groups. These low molecular mass and oligomeric compoundsare therefore referred to, inter alia, as “partially defunctionalizedamino resins”.

Low molecular mass and oligomeric compounds containing lateral and/orterminal carbamate (—HN—C(O)—O—R—O—C(O)—NH₂) groups are described in thepatents U.S. Pat. No. 5,336,566 and EP-A-0 622 387. These compounds areprepared from polyisocyanates and hydroxyalkyl carbamates. Inparticular, they enter into crosslinking reactions with amino resins.

An object of the present invention is to find new oligomeric and highmolecular mass reaction products and low molecular mass, oligomeric andhigh molecular mass compounds which offer an alternative to the existinglow molecular mass, oligomeric and high molecular mass reaction productsand/or compounds containing lateral and/or terminal carbamate groups andwhich possess a higher reactivity than these products and compoundswhile having at least the same advantageous properties as them. The newoligomeric reaction products and/or the new low molecular mass andoligomeric compounds are to be suitable for use as new advantageouscrosslinkers, and the new oligomeric and high molecular mass reactionproducts and the new oligomeric and high molecular mass compounds are tobe suitable for use as new advantageous binders for coatingcompositions, adhesives and sealing compounds, or for the production offilms.

A further object of the present invention is to provide new coatingcompositions, adhesives, sealing compounds and film precursors whichhave a new crosslinking chemistry and offer an advantageous alternativeto the existing systems.

Yet another object of the present invention is to find new, simple andelegant processes for preparing the new oligomeric and high molecularmass reaction products and/or the new low molecular mass, oligomeric andhigh molecular mass compounds.

We have found, accordingly, the novel oligomeric and high molecular massproducts of reaction of allophanic esters with nucleophilic compoundsand also the novel low molecular mass, oligomeric and high molecularmass compounds containing lateral and/or terminal allophanate groups.

We have also found the novel coating compositions, films, adhesives andsealing compounds which comprise the novel low molecular mass,oligomeric and/or high molecular mass products of reaction of allophanicesters of nucleophilic compounds and/or the novel low molecular mass,oligomeric and/or high molecular mass compounds containing lateraland/or terminal allophanate groups.

Furthermore, we have found

A) a novel process for preparing the novel oligomeric and high molecularmass products of reaction of allophanic esters with nucleophiliccompounds and/or the novel oligomeric and high molecular mass compoundscontaining lateral and/or terminal allophanate groups bytransallophanatization of hydroxyl-containing oligomers and/or polymers(nucleophiles) with alkyl and aryl allophanates,

B) a novel process for preparing the novel low molecular mass andoligomeric compounds by reacting amino resins with alkyl and arylallophanates, and

C) another novel process for preparing other novel low molecular massand oligomeric compounds by reacting polyisocyanates with hydroxyalkylallophanates.

In the light of the prior art, it was surprising and unforeseeable thatthe object on which the invention was based might be achieved with theaid of allophanates of the general formula I and allophanate groups ofthe general formulae II, III and IV:

R—O—C(O)—NH—C(O)—NH2  (I)

—O—C(O)—NH—C(O)—NH₂  (II)

—CH₂—NH—C(O)—NH—C(O)—OR¹  (III)

—O—R²—O—C(O)—NH—C(O)—NH₂  (IV)

In the general formula III, the radical R¹ denotes

an alkyl or cycloalkyl group, in particular a C₁ to C₁₀ alkyl group or aC₅ to C₁₀ cycloalkyl group; examples of suitable such groups for use inaccordance with the invention are methyl, ethyl, propyl, isopropyl,n-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, n-hexyl,2-methylhexyl, n-heptyl, 2-ethylhexyl, n-octyl, isooctyl, n-nonyl,n-decyl, cyclopentyl, cyclohexyl, cycloheptyl, indenyl or decalinylradicals;

an aryl group, in particular a phenyl group;

one of the aforementioned radicals containing essentially inert groupswhich do not react with crosslinking agents or binders; examples ofsuitable such groups are halogen atoms such as chlorine or fluorineatoms, aromatic radicals, nitro groups or alkyl or aryl ether groups;and also

one of the aforementioned groups which have at least one free hydroxylgroup, especially those derived from low molecular mass, linear orbranched polyols or from cycloaliphatic polyols; examples of suitablepolyols are neo-alcohols, butylethyl-1,3-propanediol,2-methyl-1,3-propane-diol, 1,6-hexeanediol, 1,8-octanediol,2,4-diethyl-1,3-octanediol, 2-ethyl-1,3-hexanediol,1,4-di-methylolcyclohexane, trimethylolpropane, glycerol, diglycerol,polyglycerol, pentaerythritol, dipentaerythritol or homopentaerythritol.

In the general formula IV, the radical R² denotes

linear or branched alkanediyl radicals or cycloalkanediyl radicals,especially methylene, ethylene, propylene-1,2-, tetramethylene,penta-methylene, hexamethylene, heptamethylene, cyclo-hexane-1,3-, -1,2-or -1,4-diyl, butylethyl-propane-1,3-diyl, 2-methylpropane-1,3-diyl,2,4-diethyloctane-1,3-diyl, 2-ethylhexane-1,3-diyl orcyclohexane-1,4-dimethylene radicals;

arylene radicals, especially 1,2-, 1,4- and 1,4-phenylene radicals;

the aforementioned diyl and ylene radicals which carry theabovementioned inert groups which do not react with crosslinking agentsor binders; and also

diyl radicals which still have at least one free hydroxyl group and arederived from triols and polyols, especially from trimethylolpropane,glycerol, diglycerol, polyglycerol, pentaery-thritol, dipentaerythritolor homopentaerythritol.

With the aid of these allophanates and allophanate. groups, a new kindof crosslinking chemistry is provided which yields results which isequivalent if not superior to those of the crosslinking chemistry basedon carbamates and amino resins.

In the text below, for the sake of brevity, the allophanates of thegeneral formula I are referred to as “allophanates I” and theallophanate groups of the general formulae II, III and IV are referredto respectively as “allophanate groups II, III and IV”.

Furthermore, in the text below, the novel oligomeric and high molecularmass products of reaction of allophanic esters with nucleophiles arereferred to for brevity, respectively, as “oligomeric reaction productsof the invention” or “high molecular mass reaction products of theinvention”, and the novel low molecular mass, oligomeric and highmolecular mass compounds which contain lateral and/or terminalallophanate groups are referred to correspondingly, for brevity, as “lowmolecular mass compounds of the invention”, oligomeric compounds of theinvention” or “high molecular mass compounds of the invention”,respectively.

Moreover, in the text below, for brevity, the novel process forpreparing the oligomeric and high molecular mass reaction products andcompounds of the invention by transallophanatization is referred to as“process A of the invention”, the novel process for preparing the lowmolecular mass and oligomeric compounds of the invention by reactingamino resins with alkyl and aryl allophanates is referred to as “processB of the invention”, and the novel process for preparing the lowmolecular mass and oligomeric compounds of the invention by reactingpolyisocyanates with hydroxyalkyl and hydroxyaryl allophanates isreferred to as “process C of the invention”.

In the context of the present invention, the terms “low molecular mass”,“oligomeric” and “high molecular mass” are used in their familiarsignification. In other words, the term “oligomeric” indicates that thecompound in question is composed on average of 3 to about 10 repeatingidentical basic building blocks and thus constitutes an oligomer.Accordingly, the term “high molecular mass” indicates that the compoundin question is composed on average of more than 10 repeating identicalbasic building blocks and thus constitutes a polymer, which ifappropriate may also be present in the form of highly crosslinkedparticles.

The oligomeric and high molecular mass reaction products of theinvention are formed by the reaction of nucleophiles with alkyl and arylallophanates. Depending on the nature of the nucleophile, this mayresult in a relatively wide variety of functional groups. However, thegroups in question in this case may also be the allophanate groups II,III and IV, but in particular the allophanate groups II.

The oligomeric and high molecular mass compounds of the invention areoligomers and polymers which contain the allophanate groups II, III andIV as lateral and/or terminal groups. In accordance with the inventionit is of advantage, however, if the oligomeric and high molecular masscompounds of the invention contain only at least two, preferably atleast three, of the allophanate groups II.

If the oligomeric and high molecular mass reaction products of theinvention comprise the allophanate groups II, III and IV, but especiallythe allophanate groups II, as lateral and/or terminal groups, thecompounds in question are, logically, the oligomeric and high molecularmass compounds of the invention. Since in such cases the preparation ofthe oligomeric and high molecular mass reaction products of theinvention is no different from the preparation of the oligomeric andhigh molecular mass compounds of the invention, both are dealt withtogether below under the compounds.

In special cases, it is of advantage in accordance with the invention ifthe low molecular mass and oligomeric compounds of the invention containonly at least two, in particular at least three, of the allophanategroups III or IV.

Although the preparation of the oligomeric and high molecular masscompounds of the invention containing allophanate groups II may takeplace in accordance with any desired methods, it is nevertheless ofadvantage in accordance with the invention to prepare them by process Aof the invention. To this end, oligomers and polymers which contain atleast two, preferably at least three, primary and/or secondary, butespecially primary, hydroxyl groups and which are therefore nucleophileswithin the meaning of the present invention are transallophanatized withalkyl and aryl allophanates I at from 30 to 200° C., preferably from 50to 160° C., with particular preference from 60 to 150° C., and inparticular from 80 to 140° C. The reaction is carried out in solution orwithout solvent, preferably in solution. It is advisable to addcustomary and known inhibitors such as trialkyl phosphites, especiallytriisodecyl phosphite, to the reaction mixture. It is also of advantageto use customary and known transesterification catalysts such as tincompounds, especially dibutyltin dioxide.

In the general formula I, the radical R denotes C₁ to C₁₀alkyl radicals,C₅ to C₁₀ cycloalkyl radicals or phenyl radicals. Examples of suitablesuch radicals are set out above in the context of the description of theradical R¹ of the formula III. In accordance with the invention, the C₁to C₅ alkyl radicals are of advantage in the transallophanatization andare therefore used with preference. Examples of suitable allophanates Ifor use in accordance with the invention are, accordingly, methyl,ethyl, propyl, butyl, pentyl or phenyl allophanate, of which methylallophanate and ethyl allophanate are particularly advantageous and aretherefore used with particular preference in accordance with theinvention.

As oligomers and polymers for use in accordance with the invention whichhave at least two, preferably at least three, primary and/or secondary,but especially primary, hydroxyl groups (nucleophiles), those which aresuitable include, preferably, linear and/or branched and/or block, comband/or random poly(meth)acrylates, polyesters, polyurethanes, acrylatedpolyurethanes, acrylated polyesters, polyl-actones, polycarbonates,polyethers, (meth)acrylate-diols, polyureas or oligomeric polyols.

Besides the hydroxyl groups, the oligomers and polymers may includeother functional groups such as acryloyl, ether, amide, imide, thio,carbonate or epoxide groups.

These oligomers and polymers are known to the skilled worker, and manysuitable compounds are commercially available.

In accordance with the invention, the oligomeric polyols, thepolyacrylates, the polyesters and/or the acrylated polyurethanes are ofadvantage and are therefore used with preference.

Examples of preferred oligomers and polymers for use in accordance withthe invention which have at least two, preferably at least three,primary and/or secondary, but especially primary, hydroxyl groups are

1. Oligomeric polyols obtainable by hydroformylation and subsequenthydrogenation from oligomers obtained by metathesis reactions fromacyclic monoolefins and cyclic monoolefins; examples of suitable cyclicmonoolefins are cyclobutene, cyclopentene, cyclohexene, cyclooctene,cycloheptene, norbornene or 7-oxanorbornene; examples of suitableacyclic monoolefins are present in hydrocarbon mixtures obtained inpetroleum processing by cracking (C₅ cut); examples of suitableoligomeric polyols for use in accordance with the invention have ahydroxyl number (OHN) of from 200 to 450, a number-average molecularweight Mn of from 400 to 1000 and a mass-average molecular weight M_(w)of from 600 to 1100;

2. Polyacrylates having a hydroxyl number of from 40 to 240, preferablyfrom 60 to 210, in particular from 100 to 200, an acid number of from 0to 35, glass transition temperatures of from −35 to +80° C. andnumber-average molecular weights M_(n) of from 1500 to 300 000.

The glass transition temperatures of the polyacrylates are determined,as is known, by the nature and amount of the monomers used. Theselection of the monomers may be made by the skilled worker with theassistance of the following formula V, by which the glass transitiontemperatures may be calculated approximately.

n = x 1/Tg = W_(n)/Tg_(n) ;_(n) W_(n) = 1 (V) n = 1 Tg = glasstransition temperature of the polyacrylate resin W_(n) = weight fractionof the nth monomer Tg_(n) = glass transition temperature of thehomopolymer of the nth monomer x = number of different monomers

Measures to control the molecular weight (e.g., selection ofcorresponding polymerization initiators, use of chain transfer agents,or special polymerization processes, etc.) are part of knowledge in theart and need not be elucidated here.

2.1 Particularly preferred polyacrylates are preparable by polymerizing(a1) from 10 to 92, preferably from 20 to 60% by weight of an alkyl orcycloalkyl methacrylate having 1 to 18, preferably 4 to 13 carbon atomsin the alkyl or cycloalkyl radical or mixtures of such monomers, (a2)from 8 to 60, preferably from 12.5 to 50.0% by weight of a hydroxyalkylacrylate or a hydroxyalkyl methacrylate having 2 to 4 carbon atoms inthe hydroxyalkyl radical or mixtures of such monomers, (a3) from 0 to 5,preferably from 0.7 to 3% by weight of acrylic acid or methacrylic acidor mixtures of these monomers, and (a4) from 0 to 50, preferably up to30% by weight, of ethylenically unsaturated monomers which are differentfrom (a1), (a2) and (a3) but are copolymerizable with (a1), (a2) and(a3), or mixtures of such monomers, to give polyacrylates of thespecification indicated above.

Examples of suitable (a1) components are methyl, ethyl, propyl, n-butyl,isobutyl, tert-butyl, pentyl, hexyl, heptyl or 2-ethylhexyl acrylate ormethacrylate and also cyclohexyl, tert-butyl-cyclohexyl or isobornylacrylate or methacrylate.

Examples of suitable (a2) components are hydroxyethyl, hydroxypropyl orhydroxybutyl or hydroxymethylcyclohexyl acrylate or methacrylate oradducts of (meth)acrylic acid and epoxides such as VersaticR acidglycidyl ester.

Examples of suitable (a4) components are vinylaromatics such as styrene,vinyltoluene, alpha-methylstyrene, alpha-ethylstyrene, ring-substituteddiethylstyrenes, isopropylstyrene, butylstyrene and methoxystyrenes;vinyl ethers such as ethyl, n-propyl, isopropyl, n-butyl or isobutylvinyl ether; vinyl esters such as vinyl acetate, vinyl propionate, vinylbutyrate, vinyl pivalate or the vinyl ester of 2-methyl-2-ethylheptanoicacid; or allyl ethers such as trimethylolpropane monoallyl, diallyl ortriallyl ether or ethoxylated or propoxylated allyl alcohol.

2.2 Further examples of particularly preferred polyacrylates aredescribed in the European patent application EP-A-0 767 185 and theAmerican patents U.S. Pat. Nos. 5,480,493, 5,475,073 or 5,534,598.

2.3 Further examples of particularly preferred polyacrylates are soldunder the brand name Joncryl^(R), such as, for instance, Joncry1^(R) SCX912 and 922.5.

2.4 Further examples of particularly preferred polyacrylates are thoseobtainable by polymerizing (a1) from 10 to 51% by weight, preferablyfrom 25 to 41% by weight, of 4-hydroxy-n-butyl acrylate or methacrylateor a mixture thereof, but especially 4-hydroxy-n-butyl acrylate, (a2)from 0 to 36% by weight, preferably from 0.1 to 20% by weight, of ahydroxyl-containing ester of acrylic acid or of methacrylic acid otherthan (a1), or a mixture thereof, (a3) from 28 to 85% by weight,preferably from 40 to 70% by weight, of an aliphatic or cycloaliphaticester of methacrylic acid having at least four carbon atoms in thealcohol residue, other than (a1), (a2), or a mixture of such monomers,(a4) from 0 to 3% by weight, preferably from 0.1 to 2% by weight, of anethylenically unsaturated carboxylic acid or a mixture of such acids,and (a5) from 0 to 20% by weight, preferably from 5 to 15% by weight, ofan unsaturated monomer other than (a1), (a3) and (a4), or a mixture ofsuch monomers, to give a polyacrylate having a hydroxyl number of from60 to 200, preferably from 100 to 160, an acid number of from 0 to 35and a number-average molecular weight M_(n) of from 1500 to 10 000, thecomposition of component (a3) being chosen such that polymerization ofthis component (a3) alone gives a polymethacrylate with a glasstransition temperature of from +10 to +100° C., preferably from +20 to+60° C.

Examples of suitable components (a2) are hydroxyalkyl esters of acrylicacid and methacrylic acid such as hydroxyethyl or hydroxypropyl acrylateor methacrylate, the choice being made such that polymerization of thiscomponent (a2) alone gives a polyacrylate with a glass transitiontemperature of from 0 to +80° C., preferably from +20 to +60° C.

Examples of suitable components (a3) are aliphatic esters of methacrylicacid having four to 20 carbon atoms in the alcohol residue such asn-butyl, isobutyl, tert-butyl, 2-ethylhexyl, stearyl and laurylmethacrylate; or cycloaliphatic esters of methacrylic acid on account ofcyclohexyl methacrylate.

Examples of suitable components (a4) are acrylic acid and/or methacrylicacid.

Examples of suitable components (a5) are vinylaromatic hydrocarbons suchas styrene, alpha-alkylstyrene or vinyltoluene; amides of acrylic acidand methacrylic acid such as methacrylamide and acrylamide; nitriles ofacrylic acid and methacrylic acid; vinyl ethers or vinyl esters, thecomposition of this component (a5) preferably being so apt thatpolymerization of components (a5) alone gives a polyacrylate with aglass transition temperature of from +70 to +120° C., in particular from+80 to +100° C.

2.5 The preparation of these polyacrylates is general knowledge and isdescribed, for example, in the standard work Houben-Weyl, Methoden derorganischen Chemie, 4^(th) edition, volume 14/1, pages 24 to 255, 1961.

3. Polyester resins which are preparable by reacting (a1) at least onecycloaliphatic or aliphatic polycarboxylic acid, (a2) at least onealiphatic or cycloaliphatic polyol containing more than two hydroxylgroups in the molecule, (a3) at least one aliphatic or cycloaliphaticdiol and (a4) at least one aliphatic, linear or branched saturatedmonocarboxylic acid in a molar ratio of (a1): (a2):(a3):(a4)=1.0:0.2 to1.3:0.0 to 1.1:0.0 to 1.4, preferably 1.0:0.5 to 1.2:0.0 to 0.6:0.2 to0.9 to give a polyester or alkyd resin.

Examples of suitable components (a1) are hexa-hydrophthalic acid,1,4-cyclohexanedicarboxylic acid, endomethylenetetrahydrophthalic acid,oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid,pimelic acid, suberic acid, azelaic acid or sebacic acid.

Examples of suitable components (a2) are pentaerythritol,trimethylolpropane, triethylol-ethane and glycerol.

Examples of suitable components (a3) are ethylene glycol, diethyleneglycol, propylene glycol, neopentyl glycol,2-methyl-2-propyl-1,3-propane-diol, 2-methyl-2-butyl-1,3-propanediol,2,2,4-trimethyl-1,5-pentanediol, 2,2,5-trimethyl-1,6-hexanediol,neopentyl glycol hydroxypivalate or dimethylolcyclohexane.

Examples of suitable components (a4) are 2-ethylenehexanoic acid, lauricacid, isooctanoic acid, isononanoic acid or monocarboxylic acid mixtureswhich are obtained from coconut oil or palm kernel oil.

The preparation of the polyesters and alkyd resins used with preferencein accordance with the invention is general knowledge and is described,for example, in the standard work Ullmanns Encyklopadie der technischenChemie, 3rd edition, volume 14, Urban & Schwarzenberg, Munich, Berlin,1963, pages 80 to 89 and pages 99 to 105, and also in the followingbooks: “Resines Alkydes-Polyesters” by J. Bourry, Paris, Dunod, 1952,“Alkyd Resins” by C. R. Martens, Reinhold Publishing Corporation, NewYork, 1961, and “Alkyd Resin Technology” by T. C. Patton, IntersciencePublishers, 1962.

4. Polyurethanes as described in the patents EP-A-0 708 788, DE-A-44 01544 or DE-A-195 34 361.

The resultant oligomeric and high molecular mass reaction products ofthe invention and the oligomeric and high molecular mass compounds ofthe invention which contain the allophanate groups II are outstandinglysuitable as binders for coating compositions, adhesives and sealingcompounds.

Low molecular mass and oligomeric compounds of the invention whichcontain allophanate groups III are, in particular, amino resins based onmelamine and/or benzoguanamine. Examples of suitable amino resins arehexamethylolmelamine, hexamethoxymethylmelamine,tetra-methylolbenzoguanamine, tetramethoxymethylbenzo-guanamine or theiroligomeric condensation products. In this context, all the methyloland/or methoxymethyl groups of a starting product, or only part thereof,may be converted into allophanate groups III.

These low molecular mass and oligomeric compounds of the invention maybe prepared by any desired methods. In accordance with the invention,however, it is of advantage to synthesize them by process B of theinvention. For this purpose, the amino resins are reacted in solution orwithout solvent with alkyl allophanates which in addition to theradicals R of the general formula I may also contain the radicals R¹ ofthe general formula III. It is of advantage in accordance with theinvention to conduct the reaction at from 50 to 150° C., preferably from60 to 130° C. and in particular from 80 to 120° C. A particularly goodcourse of the reaction is ensured by continually removing the waterand/or the methanol from the reaction mixture, by vacuum distillation,for example. In order to accelerate the reaction, it is also possible toadd a customary and known acidic catalyst such as p-toluenesulfonic acidto the reaction mixture.

Low molecular mass and oligomeric compounds of the invention whichcontain allophanate groups IV are, in particular, products of reactionof polyisocyanates with hydroxyalkyl and hydroxyaryl allophanates of thegeneral formula VI:

HO—R²—O—C(O)—NH—C(O)—NH—C(O)—NH₂  (VI)

Suitable hydroxyalkyl allophanates VI for use in accordance with theinvention contain the above-described radicals R², of which the ethyleneand the trimethylene radical and also the 1,4-phenylene radical areparticularly advantageous and are therefore used with very particularpreference.

Examples of suitable polyisocyanates for use in accordance with theinvention are the customary and known polyisocyanates as used, forexample, to prepare two-component coating materials, especially thosewhose isocyanate groups are attached to aliphatic or cycloaliphaticradicals. Examples of advantageous such polyisocyanates arehexamethylene diisocyanate, isophorone diisocyanate,trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanates,1,4-and 1,3-bis(isocyanatomethyl)cycloalkanes, especially 1,4- and1,3-bis(isocyanatomethyl)cyclohexane, or the adducts of thesepolyisocyanates with polyols, especially low molecular mass polyols suchas trimethylolpropane, or the polyisocyanates derived from thesepolyisocyanates and containing isocyanurate groups, uretdione groups,allophanate groups and/or biuret groups.

Where only some of the methylol and/or methoxymethyl groups of an aminoresin have been converted into allophanate groups III, the low molecularmass and/or oligomeric compounds of the invention that are in question,which contain the allophanate groups III, may be crosslinked with thelow molecular mass and/or oligomeric compounds of the invention whichcontain the allophanate groups IV, or with the oligomeric and/or highmolecular mass reaction products of the invention or the oligomeric andhigh molecular mass compounds of the invention which contain theallophanate groups II. In this way, it is possible to prepare entirelynew high-solids coating compositions, adhesives and sealing compounds orfilms, especially self-supporting paint films.

Particularly advantageous binders, adhesives and sealing compounds ofthe invention comprise as binders the oligomeric and/or high molecularmass compounds of the invention which contain the allophanate groups II.

Moreover, they comprise the customary and known amino resins and/or theabove-described low molecular mass and/or oligomeric compounds of theinvention which in which only some of the methylol and/or methoxymethylgroups have been converted into allophanate groups III. Examples ofsuitable customary and known amino resins and compounds of the inventionare those described above.

Besides these crosslinkers, further crosslinkers may also be present.Examples of suitable further crosslinkers are resins or compoundscontaining siloxane groups, resins or compounds containing anhydridegroups, resins or compounds containing epoxide groups, blocked and/orunblocked polyisocyanates and/or tris(alkoxycarbonylamino)-triazines asdescribed in the patents U.S. Pat. No. 4,939,213, U.S. Pat. No.5,084,541, U.S. Pat. No. 5,288,865 or EP-A-0 604 922.

Depending on the reactivity of the further crosslinker, it may be addeddirectly to the coating compositions, adhesives and sealing compounds ofthe invention, to give what is known as a one-component system. If, onthe other hand, it is a particularly reactive crosslinker, such as apolyisocyanate or an epoxide, it is generally not added to the coatingcompositions, adhesives and sealing compounds of the invention untilshortly before use. The result in this case is what is known as atwo-component or multicomponent system.

The coating compositions, adhesives and sealing compounds of theinvention may comprise customary and known additives in customary andknown, effective amounts.

Examples of suitable additives are polymers, crosslinkers, crosslinkingcatalysts, initiators, especially photoinitiators, pigments, dyes,fillers, reinforcing fillers, Theological assistants, solvents, wettingagents, dispersants, defoamers, adhesion promoters, additives to improvesubstrate wetting, additives to improve surface smoothness, flattingagents, leveling agents, film-forming auxiliaries, dryers, antiskinningagents, light stabilizers, corrosion inhibitors, biocides, flameretardants, polymerization inhibitors, especially photoinhibitors, orplasticizers, as are customary and known, for example, in the polymersor coatings sector.

The selection of the additives is guided by the desired profile ofproperties of the coating compositions, adhesives and sealing compoundsof the invention and by their specific end use and may therefore be madeby the skilled worker in a simple manner, possibly with the assistanceof simple preliminary tests.

The coating compositions of the invention may be present in dispersionor solution in aqueous, aqueous-organic or organic media or may bepresent as a so-called AND (non-aqueous dispersion). Furthermore, theymay be present in fine division in solid form as powder coatingmaterials or in solid forms dispersed in water as powder slurries. Theconstituents of the coating compositions of the invention that arerequired in each case are easy for the skilled worker to select on thebasis of the given profile of properties (solid, liquid, soluble inorganic solvent, water-soluble, etc.).

The coating compositions of the invention may therefore be guided fornumerous end uses. For instance, they may be used as powder coatingmaterials in industrial coating, automotive OEM coating or automotiverefinish. In these applications, their excellent storage stability ismanifested advantageously.

The particular advantages of the coating compositions of the inventionare manifested in particular in automotive OEM coating. Here, they maybe used as underbody protection, primers, soundproofing compositions,primer-surfacers, stonechip fillers, basecoat materials, solid-colortopcoat materials and/or clearcoat materials. With very particularadvantage, they are used as clearcoat materials. In this context, theymay be applied readily by the wet-on-wet technique. After baking, theirhigh level of compatibility with all customary and known basecoatmaterials, but especially with the basecoat materials of the invention,is in evidence. The clearcoats of the invention are particularlyweathering-stable and scratch-resistant.

EXAMPLES 1. The Preparation of a High Molecular Mass Compound of theInvention Containing Allophanate Groups II

1.1 Preparation of a Hydroxyl-containing Polymeth acrylate

The preparation of the polymethacrylate took place in a 4 literstainless steel reactor with stirrer, reflux condenser, one feed vesselfor monomers and one for the initiator. 930 g of solvent naphtha wereintroduced and heated to 140° C. Over the course of 4.75 hours, theinitiator feed, consisting of 167 g of solvent naphtha and 167 g oftert-butyl peroxy-2-ethylhexanoate, was metered in at a uniform rate.Over the course of four hours, the monomer feed, consisting of 348 g ofethylhexyl acrylate, 348 g of ethylhexyl methacrylate, 600 g ofhydroxyethyl methacrylate and 369 g of styrene, was metered in at auniform rate. The monomer feed commenced 15 minutes after the initiatorfeed. During the polymerization, the temperatures were held at 140° C.After postpolymerization for two hours, the reaction mixture was cooledand adjusted to a solids content of 60% by weight using solvent naphtha.The acid number was 4 and the viscosity (original) was 12 dPa.s.

1.2 The Transallophanatization of the Hydroxyl-containingPolymethacrylate With Ethyl Allophanate

469.03 parts of the hydroxyl-containing polyacrylate in accordance withexample 1.1 (60% strength in solvent naphtha), 102.4 parts of ethylallophanate and 36.7 parts of cyclohexane were charged to an appropriatesteel reactor and heated to 130° C. When they had reached thistemperature, 1.0 parts of triisodecyl phosphite and 7.4 parts of solventnaphtha were added individually. The resultant reaction mixture washeated at 130° C. for three hours.

Subsequently, 0.5 parts of dibutyltin dioxide and 7.4 parts of solventnaphtha were added and the reaction mixture was stirred at 130° C. for afurther three hours. Following this period, 5 parts of dibutyltindioxide and 7.4 parts of solvent naphtha were again added. The resultantreaction mixture was stirred at 130° C. for a further three hours.

Subsequently, volatile reaction products were removed under vacuum at115° C. and the resultant solution of the polyacrylate of the inventioncontaining the allophanate groups II was adjusted to a solids content of60% by weight using a mixture of methoxypropyl acetate and pentylacetate. The hydroxyl number (OHN) of the product was below 5.

1.3 The Preparation and the Technical Testing of a Coating Compositionof the Invention

64.8 parts of the binder of the invention in accordance with example1.2, 9.5 parts of a customary and known amino resin (Cymel 327; Americancyanamid), 1.6 parts of Tinuvin^(R) 384 (UV absorber; Ciba Geigy), 0.8parts of Tinuvin^(R) 123 (free-radical scavenger; Ciba Geigy), 1.6 partsof Nacure^(R) 4575 (catalyst; King Industries), 1.0 parts of acommercially customary leveling additive, dissolved in 0.2 parts ofxylene, 3.4 parts of n-butanol, 2.1 parts of butyl glycol acetate and14.1 parts of solvent naphtha was mixed with one another. This gave aclearcoat material which showed no increase in viscosity after 16 hoursat 60° C. or after 28 days at 40° C. This demonstrated its excellentstorage stability.

The clearcoat material of the invention was applied using a gravity flowcup gun (efflux viscosity: 28s DIN 4 cup) to test panels which had beencoated with a customary and known electrocoat (20 micrometers), acustomary and known primer-surfacer (31 micrometers) and a customary andknown basecoat (17 micrometers). In this case, the basecoat material wasapplied prior to the application of the clearcoat material and wasflashed off at room temperature for ten minutes before the clearcoatmaterial was applied.

Following its application, the clearcoat material was likewise flashedoff for ten minutes at room temperature. Subsequently, the basecoat andthe clearcoat were baked at 140° C. for twenty minutes. The resultantclearcoat had a film thickness of 28 micrometers.

Technical Tests:

The following technical tests were carried out on the test panels coatedwith the clearcoat material of the invention.

1. BART Test (Chemical Resistance)

The BART (BASF ACID RESISTANCE TEST) was used to determine theresistance of coated surfaces to acids, alkalis and water droplets.After baking, the coating was exposed to further temperature stresses ina gradient oven (30 min at 40° C., 50° C., 60° C. and 70° C.). Beforethis, the test substances (1%, 10%, 36% strength sulfuric acid; 6%strength sulfurous acid; 10% strength hydrochloric acid; 5% strengthsodium hydroxide solution; DI (i.e., deionized) water—1,2,3 or 4 drops)were applied in a defined manner using a metering pipette. Following theaction of the substances, they were removed under running water and thedamage was assessed visually after 24 h in accordance with apredetermined scale:

Score Appearance 0 no defects 1 slight marking 2 marking/dulling/nosoftening 3 marking/dulling/shade change/softening 4 cracks/incipientetching 5 clearcoat removed

Each individual marking (spot) was evaluated and the result for eachcoating was recorded in appropriate form (e.g., score totals for onetemperature).

The results can be found in table 1.

TABLE 1 Result of technical testing by the BART test Clearcoat materialof the invention Temperature (° C.) 40 50 60 H₂SO₄ 1% 0 0 0 H₂SO₄ 10% 00 0 H₂SO₄ 36% 0 0 0 HCl 10% 0 0 0 H₂SO₃ 5% 0 0 0 NaOH 5% 0 0 0 DI water1 0 0 1 DI water 2 0 0 0 DI water 3 0 0 0 DI water 4 0 0 0 Total acid 00 0 Total water 0 0 1

2. Sand Test and Brush Test (Scratch Resistance)

2.1 Sand Test

This test method tests the resistance (scratch resistance) of filmsurfaces (clearcoats and topcoats) to scratches caused by wash brushes.The method is a good imitation of the stress undergone by a film surfacein a wash installation.

In the sand test, the film surface was subjected to sand (20 g of quartzsilver sand 1.5-2.0 mm). The sand was placed in a polyethylene beaker(with its base cut off flat) which was fastened firmly to the testpanel. The test panels used were the same ones as described above in thebrush test. Using a motor drive, the panel with the beaker and the sandwas set in shaking movements. The movements of the loose sand causeddamage to the film surface (100 double strokes in 22 s). Following sandexposure, the test surface was cleaned of abraded material, wiped offcarefully under a jet of cold water and then dried using compressed air.The gloss to DIN 67530 was measured before and after damage, at 20°.

The results are given in table 2.

2.2 Brush Test

The scratch resistance of the cured coatings was assessed with the aidof the BASF brush test described in FIG. 2 on page 28 of the article byP. Betz and A. Bartelt, Progress in Organic Coatings, 22 (1993), pages27-37, albeit with modification in respect of the weight used (2000 ginstead of the 280 g specified therein), assessment taking place asfollows:

In the test, the film surface was damaged using a mesh fabric loadedwith a mass. The mesh fabric and the film surface were wetted copiouslywith a laundry detergent solution. The test panel was moved backward andforward under the mesh fabric in reciprocal movements by means of amotor drive.

The test panels were prepared by applying first an electrocoat with afilm thickness of 18-22 μm, then a primer-surfacer with a film thicknessof 35-40 μm, then a black basecoat with a film thickness of 20-25 μm,and finally the clearcoat of the invention with a film thickness of40-45 μm, each of which were cured. Following application of the coatingmaterials, the panels were stored at room temperature for at least 2weeks before testing was carried out.

The test specimen was an eraser (4.5×2.0 cm, broad side perpendicular tothe direction of scratching) covered with nylon mesh fabric (no. 11, 31μm mesh size, Tg 50° C.). The applied weight was 2000 g.

Prior to each test, the mesh fabric was replaced, with the runningdirection of the fabric meshes parallel to the direction of scratching.Using a pipette, approximately 1 ml of a freshly stirred 0.25% strengthPersil solution was applied in front of the eraser. The rotary speed ofthe motor was adjusted so that 80 double strokes were performed within aperiod of 80 s. After the test, the remaining washing liquid was rinsedoff with cold tap water and the test panel was blown dry usingcompressed air. The gloss to DIN 67530 was measured before and afterdamage (measurement direction perpendicular to the direction ofscratching).

The results of the test are likewise given in table 2.

TABLE 2 Results of the sand test and of the brush test Clearcoat ofClearcoat of the invention the invention Gloss values^(a)) Sand testBrush test Initial gloss 92 90 Residual gloss 60 58 Gloss after 2 h, 40°C. 64 61 Gloss after 2 h, 60° C. 65 64 ^(a))measured at 20° C.

The results of table 2 demonstrate the high scratch resistance of theclearcoat of the invention and its good reflow behavior.

3. Cross-cut Test

The cross-cut test was carried out in accordance with DIN ISO2409:1994-10. No delamination was observed (GT-01), which demonstratesthe excellent adhesion of the clearcoat of the invention to thebasecoat.

What is claimed is:
 1. An allophanate group-containing compoundcomprising one or more allophanate groups selected from the groupconsisting of —O—C(O)—NH—C(O)—NH₂, —CH₂—NH—C(O)—NH—C(O)—OR¹,—O—R²—O—C(O)—NH—C(O)—NH₂, and mixtures thereof, wherein R¹ is selectedfrom the group consisting of alkyl groups, cycloallkyl groups, arylgroups, and mixtures thereof, and R² is selected from the groupconsisting of linear alkanediyl groups, branched alkanediyl groups,cyloalcanediyl groups, arylene radicals, and mixtures thereof, and thetranallophanatization residue of a nucleophile comprising at least twoprimary and/or secondary hydroxy groups and which is selected from thegroup consisting of poly(meth)acrylates, polyesters, polyrethanes,acrylated polyurethanes, acrylated polyesters, polylactones,polycarbonates, polyethers, (meth)acrylatediols, polyureas, oligomericpolyols, and mixtures thereof.
 2. A method of using the compounds ofclaim 1, comprising incorporating said compounds into compositionsselected from the group consisting of coating compositions, adhesives,sealing compounds, films, and mixtures thereof.
 3. The method of usingthe compounds of claim 2 comprising incorporating said compounds ascrosslinkers.
 4. Compositions comprising the compounds of claim
 1. 5. Aprocess for preparing the compounds of claim 1 comprising thetransallophanatization of nucleophiles with alkyl and aryl allophanates.6. The compounds of claim 1 wherein R¹ comprises one or more groupsselected from the group consisting of essentially inert groups which donot react with crosslinking agents and free hydroxyl groups.
 7. Thecompounds of claim 1 wherein R² comprises one or more grops elected fromthe group consisting of essentially inert groups which do not react withcrosslinking agents and free hydroxyl groups.
 8. The compounds of claim1 which have from 3 to 10 repeating identical basic building blocks. 9.The compounds of claim 1 which have more than 10 repeating basicbuilding blocks.
 10. The compositions of claim 4 which are selected fromthe group consisting of coating compositions, film forming compositions,adhesive compositions, sealing compounds, and mixtures thereof.
 11. Aprocess for preparing compounds comprising lateral and/or terminalallophanate groups, comprising reacting polyisocyanates with hydroxyfunctional allophanic esters selected from the group consisting of alkylallophanates, cycloalkyl allophanates, aryl allophanates, and mixturesthereof.
 12. Compounds comprising lateral and/or terminal allophanategroups, comprising the reaction product of allophanic esters selectedfrom the group consisting of alkyl allophanates, cycloalkylallophanates, aryl allophanates, and mixtures thereof with nucleophiliccompounds, wherein the compounds have from 3 to 10 repeating identicalbasic building blocks.
 13. Compositions comprising the compounds ofclaim
 12. 14. Compositions according to claim 13, selected from thegroup consisting of coating compositions, film forming compositions,adhesive compositions, sealing compounds, and mixtures thereof. 15.Compounds comprising lateral and/or terminal allophanate groups,comprising the reaction product of allophanic esters selected from thegroup consisting of alkyl allophanates, cycloalkyl allophanates, arylallophanates, and mixtures thereof with nucleophilic compound, whereinthe compounds have more than 10 repeating identical basic buildingblocks.
 16. Compositions comprising the compounds of claim
 15. 17.Compositions according to claim 16, selected from the group consistingof coating compositions, film forming compositions, adhesivecompositions, sealing compounds, and mixtures thereof.